If we call another extension internally, they will hear us but we cannot hear them.

If someone calls in from outside and gets the auto attendant, no input is accepted, the attendant just keeps going. (i.e. Press 2 for this, she just keeps going, you can press as many buttons as you like, no change).

The solution seems to be to reboot the main 2801 with the PRI. I am not sure why this would cure internal extension-to-extension calls, but it does. My facility runs 24 hours a day, so a reboot is never a good thing.

Where should I start looking? Broadcast storms? Is this a sort of known bug that Cisco might have fixed somewhere? Anything in Unity or CCM I should look at? Counters on ports?